1. Field of Application
The present invention relates to a control apparatus for a polyphase synchronous rotary machine, and in particular to a control apparatus for operating the rotary machine such as to reduce vibration of the rotor and thereby reduce consequent audible noise produced from the rotary machine.
2. Background Technology
Technology is known, as described in Japanese patent publication No. HEI 11-55986 (designated in the following as reference document 1), for reducing the torque ripple of a permanent magnet type of rotary machine. With that technology, data are stored in a memory apparatus expressing torque ripple, such as cogging torque (caused by circumferential variations in magnetic permeance of the stator, due to the wiring slots in the stator iron core). Based on the stored torque data, sinusoidal-waveform currents which flow in the stator windings are compensated such as to reduce the torque ripple.
However when currents are passed through the windings of the stator of a synchronous rotary machine for driving the rotor, varying (i.e., rotating) electromagnetic forces are applied to the rotor, acting (alternately attracting and repelling) in directions at right angles to the rotor axis. When such a varying electromagnetic force has a frequency that is close to a resonance frequency of a vibration mode of the rotor, large-amplitude vibration of the rotor may occur. A high level of audible noise is thereby generated by the rotary machine.